NO SWEAT: Although Yankees GM Brian Cashman has been spurned by Cliff Lee, as forwarned by The Post last Friday, thesse Phillies fans are likely thrilled that the lefty is now part of their amazing rotation. Photo: Anthony J. Causi

This is an era in Yankees history that will be defined by what they have done without Cliff Lee.

Because twice, they were on the doorstep of acquiring the ace and now have twice been spurned — or two more times than they anticipated.

They had a deal in principle to obtain Lee from the Mariners in July and had him slip away to the Rangers. And they just had him slip away in free agency despite outbidding the winning Phillies by about $50 million.

Maybe the Yankees will look back in several years and be happy about the prospects they did not give up in July for Lee. Maybe they will look back in several years and be thrilled that they did not do a seven-year deal with Lee because the lefty did not survive that tenure well.

But in the present tense, the double-barrel rejection feels overwhelming. First, because the Lee-led Rangers beat the Yankees in the ALCS last season. Second, because the Yankees now must move forward without having filled the most obvious need for next season, a high-end starter. So though the 2014 Yankees might benefit from not having another high-paid, aging player such as Lee, the 2011 Yankees are sure to be hurt by his absence.

And Philadelphia is sure to benefit. Like the Red Sox, the Phillies have found their inner Yankees. Both the Red Sox and Phillies will at least approach the Lee-less Yankees for highest payroll in the sport and also for star power and now expectations.

The Phillies have now —amazingly — obtained Lee (twice), Roy Halladay and Roy Oswalt since the Yankees signed CC Sabathia. Lee, Halladay, Oswalt and Cole Hamels project to form one of the best rotations in major-league history, making this a bad day for New York baseball all around because the Mets reside in the NL East.

The Yankees, on the other hand, have a rotation with Sabathia coming off of knee surgery and the heaviest work load in the sport the past four years, and even larger questions beyond that. Those questions were manifest enough last season that Yankees general manager Brian Cashman was willing to include his best prospect, Jesus Montero, in a package for Lee.

Initially, Seattle agreed. But they Mariners backed out over concerns about prospect David Adams’ medical records. The Mariners indicated they would reconsider if the Yankees put either Eduardo Nunez or Ivan Nova in the deal instead. Cashman refused, saying it was too much for half a season of Lee.

But that decision might be the costliest of this era. Because with Lee, the Yankees and Rangers probably would have had different postseason fates and the Yankees just might have repeated as champs. Also, Lee would have experienced New York. That means he might have built the love for the place that he did for Philadelphia.

That love led Lee to take so much less to go back to the Phillies. The Yankees’ biggest offer was $154 million over seven years, which included a $16 million player option in the final season. It is believed Lee accepted only five guaranteed seasons at around $20 million annually, with a sixth-year player option. Which is stunning considering that this is an offseason when money is flowing large again, and Lee was viewed as the ultimate mercenary.

And the Yankees have the most money, which made them confident that even after losing Lee last July they would win for him this offseason. But those plans were dashed shockingly by the Phillies’ late, determined run.

Now the Yankees just don’t have a Plan B for healing their rotation. They do not believe the next best starter available, Kansas City’s Zack Greinke in a trade, can handle New York. The other current possibilities are more mid- to back-end guys like Gavin Floyd or Edwin Jackson.

The Yankees will say now they are relieved because, by leaving so many dollars on the table, Lee was signaling he really did not want New York. They will say they were uncomfortable going to age 39 with a pitcher who had back problems last year or that they have some of the best pitching prospects in the majors coming or they now have great financial flexibility to pounce on what they want during the year.

But that is all spin that could be heard a lot in the future of what has become The Not Cliff Lee Era for the Yankees.